1. Field of the Invention:
The invention relates to a spring biased temperature probe for sensing the disc cavity temperature of a gas turbine engine and more particularly to a self-contained assembly of such a probe to ensure a predetermined amount of slack in the lead wires of the probe to prevent failure of the probe due to fatigue or stress on the wires and to permit a sealed engagement between the probe and an internal cylinder.
2. Description of the Prior Art
Thermocouples are generally used to measure the temperature in certain critical areas of high temperature turbo-machinery. One such area is the discs of a gas turbine engine, and, in sensing such temperature, it is common to place a temperature probe so that the thermocouple tip is disposed in the disc cavity adjacent the rotor disc.
In the gas turbine of the assignee of the present invention, the temperature probe has typically extended from the turbine cylinder inwardly through an inner cyinder defining a cooling air chamber supplying cooling air for the hollow vanes supported on a blade ring and extended further inwardly through said hollow vane to ultimately position the thermocouple tip adjacent the face of the downstream rotor disc. (A more detailed description, which is also the closest known prior art, will be discussed in the following description of the preferred embodiment).
The tube or conduit housing the thermocouple leads is tapered at an intermediate position to sealingly engage a similarly tapered aperture in the inner cylinder as biased by a coil spring. The tube also is divided into two sections (i.e. an upper and lower section) with the upper section extending into the probe head where the lead wires were connected to terminals on a ceramic board housed therein. The upper and lower sections preferably have adjacent ends disposed in a cavity defined by the flange member mounting the probe to the turbine cylinder. This cavity provides a space for coiling the lead wires to provide sufficient slack therein so that vibrations in the lower shaft and leads are not transmitted to the terminal or the ceramic board in the head. However, it has been found that the prior arrangement is cumbersome and has inherent assembly difficulties especially evident when the assembly is being mounted on the turbine cylinder. At times this results in the leads being made taut in the flange cavity, resulting in failures of the probe due to vibrational and other stress which the probe was not designed to encounter.
Further, in shipping and handling the prior assemblies, the lower shaft of the probe is sufficiently movable such that at times the weight of the shaft is supported by the thermocouple wires causing them to break.